Microphone



Jan. 17, 1928. 1,656,425

I B. E. COVER 7 MICROPHONE Filed Jqly 22. 1922 Patented Jan. 17, 1 928.

UNITED s AT s COVER, OF CHICAGO, ILIINOIS.

moaornomr.

' Application filed July 22,

This invention relates to microphones and" has for its principal object to magnify the changes in resistance caused by vibratory movements.

A further object of the invention is to resolve the vibrations into movements in a plurality of directions whereby. the changes in thearea of contact are increased to pro duce corresponding changes in the resistance and the current.

A further object of, the invention is to produce a microphone including granules of conductive material and a movable electrode which is operated by motion having a tend:

ency to give a rolling action on the granules.

A further object of the invention is to provide a reproducer vfor phonographs involving the microphone principle and operating with high efiiciency.

Further objects and advantages of the invention will become apparent as the description is read in connection with the accompanying drawing illustrating a selected emodiment ofthe invention, and in which 35 Fig. 1 is a side elevation of a reproducer for phonographs embodying the principles of this invention; l y a Fig. 2 is-a transverse section on the line 2-2 of Fig. 1; v

the line 3-3 of Fig. 1; and

of Fig. 2.

Referring to the referencenumerals on the 35 drawing, 10 indicates a base, here shown in theform of a disc, having a tubular flange 11 surrounding a a central opening and a curved flange 12 at its periphery. Secured to the base in any suitable manneris a plate 13 of-fibre' or any other insulating material and in this plate are seated a. plurality of cups 14. As shown, each of these cups comrises a threaded sleeve or lnipple 15 screwed mto a recess in theplate 13 surrounding a 5 cylinder of loose asbestos 16,-" within which is a suitable quantity of granular conductive material such as .carbon or coke 17 adapted to be compressed between a fixed electrode 18 and amovable electrode 19, the

so two electrodes 19 lying in substantially the same plane. The electrode 18 is preferably of carbon .and is held in place by a screw 20 which may be also u ed to electrically counect the corresponding electrodes of a pair 55 of microphones together as by lIlSBItlDg mechanism. .equlpped with cars 33 or other su1table means for receiving screws 34 which have Fig. 3 is a vertical longitudinal section on screws through a metallic bar 21 (Fig. 4). The electrode 19 is preferably a copper plated carbon disc, and each of the four such electrodes is connected by a screw 22 to a yoke 23, which in this instance happens to be H-shaped. A disc 24 of mica or other suitable material rests on the electrode 19 and is clamped between the electrode and a metallic disc 25 which in turn is spaced from the yoke 23 by a washer 26. The

screws 22 pass through the electrodes 19, the mica d1sks 24, the metallic disks 25, the

washers 26 and the arms of the yoke 23 and receive on their outer ends conical nuts 27. The wings 28 and 29 of the yoke 23 thus make electrical connection between ,electrodes 19 corresponding to the two electrodes 18 that are connected b the bars 21.

Seczured to diametrica ly opposite points on the plate 13 byscrews 30 is a U-shaped frame 31 having a tubular flange 32 adapted to make connection with the phonograph This frame is preferably reduced extensions 35 and shoulders 36 adapted to cooperate with springs 37 rest- Q ing on the ends of the wings 28 and coiled about the conical nuts 27 and the'projectin ends of the screws 22. These screws 34 and sprin s 37 permit the normal pressure of the mova le electrodes 19 on the granules to be varied to suit particular conditions.

The tubular flange 11 is fitted with a liner 38 held in place by a set screw 57 and having an internal flange 39 and a trans: verse passage adapted to receive the pivot 40 of a stylus bar '41 which may be equipped with a suitable bushing. 42. i The lower end of this stylus bar has the usual opening for receiving a stylus that is secured in place by the set screw 43. The upper end is reduced and threaded at 44 to receive a nut 45 for connecting it with the body portion 46 of the yoke 23. In order to insulate the stylus bar :from the yoke, I provide two fibre washers 47 and 48 which cooperate with the tube 49 to prevent contact between the body portion 46 on the yoke and the stylus bar. For convenience a metallic connection 50 is perforated to receivethe tube 49 and is clamped against the body portion 46 by thewashers 47 and 48.

The connecting bars 21 are preferably equipped with arms 51. which have suitable fasten ngs 52 to receive the cables 53 and 54 which may be in addition soldered to the arms 51 as indicated at 55. The connection 50 is similarly attached to the third cable 56.

It will be noted that the mica discs 24 extend over the edges of the nipples 15 a sufiic'ent distance to permit lateral movement of the discs without e osing the interior of the carbon cups. he reason for this will be apparent from the fact that when the stylus bar 41 vibrates about its pivot it will move the yoke sidewise as well as up and down in Figs. 1, 3 and 4, which will cause'the mica discs and the electrodes 19 to move across the carbon cups as well as axially with respect thereto. As a result the electrodes 19 will in addition to compressing the carbon or other granules give, them a rolling action that will tend to move them to positions in which the area of contact is relativel great. This will increase the conductivity of the granules and therefore the current passing through them.

When the stylus bar swings in one direction, the wing 280i the yoke will move its electrodes 19 to compress'and roll down the carbon granules in two of'the cups, while the wing 29 will execute thereverse movement releasing the pressure of the granules in the other cups and give them a slight rolling movement tending. to loosen them up. I have found in practice that by transmitting the vibratory motion to the carbon cups in this manner the changes in resistance are greatly magnified resulting in corresponding amplification of sounds or other sources of minute vibratory movement. The asbestos is preferably in a fiuffy condition and held together by small, slight threads. or the like, so that its cushioning effect is not reduced. The presence of this lining of asbestos assists in preventing the granules from packing and also allows for expansion due to heating.

The embodiment here illustrated givies very gratifying results in connection with a phonograph record and those skilled in the art will readily find a variety of other applications for principles of the invention.

I am aware that changes may be made in the form, construction and arrangement of the invention, as set forth in the selected end of said cup, a yielding disc secured to the electrode and closing said cup, and means for giving said movable electrode motion transversely with respect to said cup, to give a rolling movement to said granules.

2. In a reproducer, the combination of a plurality of microphones, each including a carbon cup, carbon granules therein, a fixed movable electrodes and the covers together,

and a pivoted stylus bar operatively con-' oted to said base and operatively connected to sa d yoke.

4. In a reproducer, the combination. of a plurality of spaced microphones, each including granules of conductive material and a movable electrode, a yokeconnecting said electrodes at the top thereof, a horizontal pivot below the electrodes and opposite the space therebetween, and astylus bar electrode, amovable electrode and a yielding cover for said cup, means for connecting the mounted on said pivot and arranged to swing in said space and connected to said yoke intermediate of said electrodes.

5. In a reproducer, the combination of spaced microphones, each including fixed and movable electrodes operating upon granules of conductive material, independent cables connected with said fixed elec trodes, a common cable connected with said movable electrodes, and a pivoted stylus bar adapted to give said movable electrodes a compression and a sidewise motion along the surface of said granules. V

6. In a reproducer, the combination of a base, an insulating plate carried thereby, a plurality of microphones carried by said plate, each including a movable electrode, means for connect-ing said electrodes together, means for adjusting the pressure of said electrodes, and means for giving said electrodes a compressing and a rolling movement.

7. Ina reproducer, the combination of a base, a plurality of microphones carried by said base, each including a movable electrode, a yoke connecting said movable electrodes, a frame attached to said base, and means carried by said frame for adjusting the pressure of said movable electrodes.

8. In a reproducer, the combination of a plurality of microphones, each including a cup, granules of conductive material in said cup, a movable electrode in said cup, a flexible cover for said cup, means for connecting said movable electrodes and covers together, and means for giving said movable electrodes a compressing and a lateral movement.

9. In a reproducer, the combination of a base, a plurality of cups supported on said base, each cup containing granules of conductive material and movable electrodes resting on the granules in each cup, means connecting said electrodes together, means for moving said electrodes along the surface of said conductive material and means for exerting a pressure on said electrodes to compress said conductive material.

10. In a reproducer, the combination of a base, a plurality of cups supported on said base, each cup containing granules of conductive material and movable electrodes resting on the granules in each cup, means connecting said electrodes together, means for moving said electrodes along the surface of said conductive material and means tor exerting a pressure on said electrodes, and

means for adjusting said pressure means to vary the pressure exerted on said conductive material by said electrodes.

11. In a microphone, the combination of a cup, granules of conductive material in said cup, a movable electrode contacting with the surface of said granules, means for giving said electrode a movement along the surface of said granules and means for exerting pressure on said electrode to compress said granules.

12. In a microphone, the combination of a cup, granules of conductive material in said cup, a movable electrode contacting with the surface of said granules, means for giving said electrode a movement alongthe surface of said granules and means for exerting pressure on said electrode to com ress said granules and means to adjust sai last named means, to vary the amount of pressilire exerted by said electrodes on said granu es.

BERKEY E. COVER. 

